Direct laryngoscopy and endotracheal intubation is an indispensable procedure in contemporary healthcare, with millions of patients being intubated each year. Because intubation invariably results in cervical spine movement, it is considered to be hazardous in patients with cervical spine instability, carrying a risk of catastrophic spinal cord injury (quadriplegia or death). Our long-term goal is to increase the safety of endotracheal intubation in patients with cervical spine instability. Current clinical standards for intubation in the presence of cervical spine instability are not evidence-based because, in large part, previous studies have not studied intubation from a biomechanical perspective. The relationships between forces applied to the peri-airway tissues and cervical spine during intubation and the resulting motion are not known. Consequently, it is not known (1) which forms of cervical spine instability present the greatest risk of neurologic sequelae, and (2) which intubation techniques and devices minimize cervical spine movement and the possibility of spinal cord compression. To fill this knowledge gap, the aims of this project are to quantify the pattern of cervical spine motion that results from the specific forces applied to the peri-airway tissues during intubation. We will simultaneously measure cervical spine motion (lateral x-rays), applied forces (force-sensing laryngoscopes), and view of the airway (video) during intubation. These measurements will be made in (1) living anesthetized humans with stable spines and (2) in cadavers with stable and unstable spines. We will then utilize all of the information derived from these studies to complete and verify a three-dimensional model of the human cervical spine. The model will be used to (1) indentify which types of cervical spine instability are most dangerous in terms of intubation, (2) determine how current and future intubation devices can be most safely used to accomplish intubation while minimizing dangerous motion, and (3) develop new protocols that ultimately lead to safer patients intubations in the presence of unstable cervical spines.